//copy更像插入

var buf1 = Buffer.from('abcde','utf-8');
var buf2 = Buffer.from('hell world','utf-8');

//将 buf2 插入到 buf1 指定位置上
buf2.copy(buf1,1,0,buf2.length);//buf.copy(targetBuffer, targetStart, sourceStart, sourceEnd)无返回值
//受限于目标：buf1的长度为5，故新的buf为ahell

console.log(buf1.toString());